Depending on the requirements placed on the coloring result, a person skilled in the art is aware of various coloring systems for providing color-modifying cosmetic agents, in particular for keratinic fibers, such as for example hair. “Oxidation coloring agents”, as they are known, are used for permanent, high intensity coloring results with corresponding fastness characteristics. Such coloring agents conventionally include oxidation dye precursors, known as “developer components” and “coupler components” which, under the influence of oxidizing agents such as for example hydrogen peroxide, react with one another to form the actual dyes. Oxidation coloring agents are distinguished by excellent, long-lasting coloring results. In addition to coloring, many consumers very specifically also wish to achieve lightening or blonding of their own hair color. To this end, the natural or artificial dyes coloring the fibers are decolorized, usually oxidatively using appropriate oxidizing agents, such as for example hydrogen peroxide.
In order to achieve optimum coloring and lightening performance, oxidative coloring or lightening agents generally require an alkaline pH value in use, optimum results in particular being achieved at pH values between 8.5 and 10.5.
Hydrogen peroxide is used as standard as an oxidizing agent both in oxidative coloring and in lightening or blonding of keratinic fibers. Aqueous hydrogen peroxide solution are, however, unstable at the alkaline pH values required for use, such that conventional commercial oxidative coloring and blonding products generally consist of at least two components. The first component is an acidified oxidizing agent preparation including hydrogen peroxide which is mixed shortly before use with an alkalized second component which for example assumes the form of a cream. In the case of an oxidative coloring product, said second component additionally includes oxidation dye precursors of the developer and/or coupler type.
The components can be mixed with the assistance of various mixing devices. One mixing method which is well-established primarily among home users is to transfer the two components into an applicator bottle, mix them to form a homogeneous formulation for use by shaking the bottle and then apply them onto the keratin fibers via an orifice in the applicator bottle. In another mixing method which is often used by hairdressers, the two components are placed in a mixing dish from where, once they have been carefully stirred or mixed together, they are applied onto the hair with the assistance of a paintbrush or an applicette.
Both methods place specific requirements on the packaging and viscosity of the formulations used in each case, wherein both the viscosities of the individual components (oxidizing agent preparation and alkaline (cream) component) and the viscosity of the final mixture for use make a substantial contribution to achieving a uniform and intense coloring or lightening result.
If, in the case of mixing in a mixing dish, individual formulations with excessively different viscosities are mixed together, blending to form a homogeneous formulation for use can be achieved only with difficulty or only after extended stirring. The viscosities of the oxidizing agent preparation and alkaline (cream) component must therefore be precisely adjusted to one another. In particular if one or both of the formulations used have an excessively high viscosity and are thus much too viscous, complete intermixing by stirring with a paintbrush can only be achieved with difficulty.
Furthermore, it must be ensured that the oxidizing agent preparation can be optimally discharged from the container in which it was provided for use. Said container usually comprises a flexible bottle with a small orifice from which the oxidizing agent preparation can be discharged by squeezing the bottle. Oxidizing agent preparations with an excessively high viscosity can be discharged only slowly, incompletely and by applying elevated pressure to the bottle.
Low-viscosity formulations can be transferred more readily from the bottle into the mixing dish, but are disadvantageous during subsequent mixing with the usually creamy, relatively high viscosity second component.
The viscosities of formulations which are intended to satisfy all the above-stated requirements, must therefore reliably be in a defined range which permits only a slight range of variation towards higher or lower viscosities.
The viscosity of formulations can be adjusted by using polymeric thickeners. If the viscosity of formulations including oxidizing agents is to be controlled, the thickener used must additionally be stable towards oxidizing agents.
Homo- and copolymers of acrylic acid or of methacrylic acid have hitherto proven to be the thickener system of choice for oxidizing agent formulations including hydrogen peroxide. Acrylic acid polymers and corresponding derivatives have elevated stability towards hydrogen peroxide, provide reliable thickening precisely in an alkaline environment and are compatible with electrolytes, salts and polar solvents.
Uncrosslinked or crosslinked polyacrylic acid polymers are used, for example in DE 10 2010 003 263 A1 and in DE 37 32 147 A1, for thickening oxidizing agent preparations. The oxidizing agent preparations described in DE 10 2010 003 264 A1 are biphasic systems which likewise include polyacrylic acid polymers for adjusting viscosity. Due to their poor biodegradability, however, efforts are increasingly being made to reduce the quantity of acrylic acid polymers used in cosmetic products or to replace them completely by natural thickeners or swelling agents with an improved environmental profile. Natural swelling agents, however, have the disadvantage that, if used in an excessively large amount, they can easily form a film on the skin. Such residues are not desired by consumers. If, on the other hand, the usage concentration of the biological swelling agents is reduced to such an extent that no residues remain on the skin after use, there is a risk that the viscosity cannot reliably be adjusted to the desired value over an extended storage period or the formulations will remain too thin.
It is therefore desirable to provide oxidizing agent preparations which make it possible to dispense with synthetic polymers, in particular polyacrylic acids, as a formulation component. It should here be possible reliably to adjust the viscosity of these formulations in such a manner that optimum intermixability with an alkaline (cream) component is ensured. Furthermore, it should be possible to discharge the oxidizing agent preparation completely from the container in which it is provided.
After intermixing, the formulation for use should have a viscosity which permits convenient application of the formulation onto the keratin fibers, wherein it should be possible for the formulation for use to be effectively distributed and give rise to uniform color change while, however, not dripping down from the consumer's head. Furthermore, all the thickeners used for adjusting viscosity should be biodegradable and not remain in the form of residues on the consumer's skin after use.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.